Hip biomechanics in early recovery following fixation of intertrochanteric fractures: Results from a randomised controlled trial.

Single and dual integrated screw femoral nails are both commonly used to treat intertrochanteric fractures. This study investigated if using single or dual integrated screw femoral nails result in different post-operative hip joint loading. In the presence of differences, we investigated potential contributing factors. Patients were randomised for treatment via single screw (Stryker, Gamma3) or dual-integrated screw nail (Smith and Nephew, Intertan). Pre-injury mobility levels were collected at enrolment. Hip radiographs and gait data were collected at six weeks (Gamma: 16; Intertan: 15) and six months (Gamma: 14; Intertan: 13) follow-up. The resultant hip joint reaction forces and abductor muscle forces were estimated using electromyography-assisted neuromusculoskeletal modelling during level walking gait. Our primary analysis focused on the resultant hip joint reaction force and abductor muscle forces. We compared between groups, across stance phase of walking gait, using statistical parametric mapping. At six weeks, the Intertan group showed a short (∼5% of stance phase) but substantial (33 % [0.3 × body weight] greater magnitude) resultant hip joint reaction force when compared to the Gamma group (P = 0.022). Higher gluteus medius forces (P = 0.009) were demonstrated in the Intertan group at six weeks. Harris Hip Scores followed the trend seen for the biomechanical outcomes with superior scores for the Intertan group at six weeks postoperative (P = 0.044). The use of dual-integrated screw femoral nails over single screw devices may allow for hip biomechanics more closely resembling normal hip function at earlier post-operative timepoints, but these appear to resolve by six months postoperative.

Corroboration of coupled musculoskeletal model and finite element predictions with in vivo RSA migration of an uncemented acetabular component.

While finite element (FE) models have been used extensively in orthopedic studies, validation of their outcome metrics has been limited to comparison against ex vivo testing. The aim of this study was to validate FE model predictions of the initial cup mechanical environment against patient-matched in vivo measurements of acetabular cup migration using radiostereometric analysis (RSA). Tailored musculoskeletal and FE models were developed using a combination of three-dimensional (3D) motion capture data and clinical computerized tomography (CT) scans for a cohort of eight individuals who underwent primary total hip replacement and were prospectively enrolled in an RSA study. FE models were developed to calculate the mean modulus of cancellous bone, composite peak micromotion (CPM), composite peak strain (CPS) and percentage area of bone ingrowth. The RSA cup migration at 3 months was used to corroborate the FE output metrics. Qualitatively, all FE-predicted metrics followed a similar rank order as the in vivo RSA 3D migration data. The two cases with the lowest predicted CPM (<20 µm), lowest CPS (<0.0041), and high bone modulus (>917 MPa) were confirmed to have the lowest in vivo RSA 3D migration (<0.14 mm). The two cases with the largest predicted CPM (>80 µm), larger CPS (>0.0119) and lowest bone modulus (<472 MPa) were confirmed to have the largest in vivo RSA 3D migration (>0.78 mm). This study enabled the first corroboration between tailored musculoskeletal and FE model predictions with in vivo RSA cup migration. Investigation of additional patient-matched CT, gait, and RSA examinations may allow further development and validation of FE models.

The absence of reporting standards and a lack of objective, performance-based outcomes following intramedullary nailing of tibial shaft fractures: findings from a scoping review into 179 articles.

PURPOSE: This scoping review was conducted to summarise the outcome tools reported in the assessment of tibial shaft fractures treated with intramedullary (IM) nailing, with a key focus on knee pain and function, and performance-based outcomes. METHODS: PubMed and Embase databases were searched on May 31, 2023. All study designs and populations were included, including ex vivo studies without fracture. Studies with only open or intra-articular fractures, or other fracture fixation, were excluded. Reported outcome tools and pertinent study characteristics were extracted and summarised. RESULTS: Of 488 articles identified, 179 met the inclusion criteria. For in vivo studies (n = 152), there were 13,705 fractures; the IM nailing approach not described for 30% of these. There were 133 unique patient outcomes, with a binary assessment of knee pain (29% of studies) and Lysholm score (21%) most common. Only 10/152 (7%) in vivo studies included an objective, performance-based measure of knee function. Fracture union was most frequent (52%) of 81 different clinical outcomes. For ex vivo studies (n = 29), there were 408 tibias included, with nail insertion location most prevalent (66% of studies) of 34 reported outcomes. CONCLUSION: The heterogeneity of outcome tools reported limits comparison between studies and the most commonly reported patient outcomes may not be the most appropriate. Future studies should report the IM nailing approach and consider capturing both patient-reported and performance-based outcomes to help inform surgical decision making.

Optimizing Wearable Device and Testing Parameters to Monitor Running-Stride Long-Range Correlations for Fatigue Management in Field Settings.

PURPOSE: There are important methodological considerations for translating wearable-based gait-monitoring data to field settings. This study investigated different devices' sampling rates, signal lengths, and testing frequencies for athlete monitoring using dynamical systems variables. METHODS: Secondary analysis of previous wearables data (N = 10 runners) from a 5-week intensive training intervention investigated impacts of sampling rate (100-2000 Hz) and signal length (100-300 strides) on detection of gait changes caused by intensive training. Primary analysis of data from 13 separate runners during 1 week of field-based testing determined day-to-day stability of outcomes using single-session data and mean data from 2 sessions. Stride-interval long-range correlation coefficient α from detrended fluctuation analysis was the gait outcome variable. RESULTS: Stride-interval α reduced at 100- and 200- versus 300- to 2000-Hz sampling rates (mean difference: -.02 to -.08; P ≤ .045) and at 100- compared to 200- to 300-stride signal lengths (mean difference: -.05 to -.07; P < .010). Effects of intensive training were detected at 100, 200, and 400 to 2000 Hz (P ≤ .043) but not 300 Hz (P = .069). Within-athlete α variability was lower using 2-session mean versus single-session data (smallest detectable change: .13 and .22, respectively). CONCLUSIONS: Detecting altered gait following intensive training was possible using 200 to 300 strides and a 100-Hz sampling rate, although 100 and 200 Hz underestimated α compared to higher rates. Using 2-session mean data lowers smallest detectable change values by nearly half compared to single-session data. Coaches, runners, and researchers can use these findings to integrate wearable-device gait monitoring into practice using dynamic systems variables.

Deep Metric Learning for Scalable Gait-Based Person Re-Identification Using Force Platform Data.

Walking gait data acquired with force platforms may be used for person re-identification (re-ID) in various authentication, surveillance, and forensics applications. Current force platform-based re-ID systems classify a fixed set of identities (IDs), which presents a problem when IDs are added or removed from the database. We formulated force platform-based re-ID as a deep metric learning (DML) task, whereby a deep neural network learns a feature representation that can be compared between inputs using a distance metric. The force platform dataset used in this study is one of the largest and the most comprehensive of its kind, containing 193 IDs with significant variations in clothing, footwear, walking speed, and time between trials. Several DML model architectures were evaluated in a challenging setting where none of the IDs were seen during training (i.e., zero-shot re-ID) and there was only one prior sample per ID to compare with each query sample. The best architecture was 85% accurate in this setting, though an analysis of changes in walking speed and footwear between measurement instances revealed that accuracy was 28% higher on same-speed, same-footwear comparisons, compared to cross-speed, cross-footwear comparisons. These results demonstrate the potential of DML algorithms for zero-shot re-ID using force platform data, and highlight challenging cases.

Retention of kinematic patterns during a 6-minute walk test in people with knee osteoarthritis.

BACKGROUND: Knee osteoarthritis (OA) is a chronic condition affecting the entire joint and surrounding tissue, resulting in pain, stiffness and impaired movement. Recent studies have suggested the use of physical performance tests, such as the six-minute walk test (6MWT) to assess joint function for those with knee OA. This study assessed lower limb sagittal plane joint angles during a 6MWT for people with mild-moderate knee OA. METHODS: Thirty-one participants (18 male, 13 female; 62.9 ± 8.4 years) with knee OA were recruited. Gait data were collected in a single session during which participants completed a 6MWT around a 20 m course. Sagittal plane joint angles for the hip, knee and ankle were calculated during the first and last minute of the 6MWT. Statistical parametric mapping (SPM) was used to investigate changes in kinematic traces over the gait cycle. RESULTS: Mean joint angles for the hip and knee showed no significant differences between the first and last minute of the 6MWT. Ankle joint kinematic traces indicated there to be a decrease in plantarflexion approaching toe-off in the last minute of the test - a 1.5° reduction from the first minute. No significant differences were calculated for walking speed or joint range of motion. DISCUSSION: The lack of significant change in joint kinematic parameters and walking speed suggests the relative fatigue and pain burden to the participant over the duration of the 6-minute period is insufficient to elicit any mechanical changes to walking gait.

The role of muscle forces and gait cycle discretization when assessing acetabular cup primary stability: A finite element study.

The aim of this study was to investigate the influence of the muscle force contribution and loading cycle discretization on the predicted micromotion and interfacial bone strains in the implanted acetabulum. To this end, a patient specific finite element model of the hemipelvis was developed, based on the CT-scan and gait analysis results, collected as part of the authors' previous work. Outcomes of this study suggests that the acetabular cup micromotion and interfacial bone strains can be predicted just using the joint contact force. This helps to reduce the complexity of the finite element models by ignoring the contribution of muscle forces and the associated challenges of mapping these forces to the pelvis. However, the gait cycle needs to be adequately discretised to capture the micromotion at the bone-implant interface. BACKGROUND AND OBJECTIVE: The Dalstra load case, which includes muscle forces, has been widely adopted in the literature for studying the mechanical environment in the intact and implanted acetabulum. To simplify the modelling approach, some researchers ignore the contribution of muscle forces. The Dalstra load case is also divided into eight separate load steps (five in the stance phase and three in the swing phase), however, it is unclear whether this adequately captures the micromotions, for a cementless acetabular cup, during a simulated activity. The aim of this study was to investigate the influence of the muscle force contribution and loading cycle discretization on the predicted micromotion and interfacial bone strains. METHODS: In this work, a patient specific finite element model of the hemipelvis was developed, based on the CT-scan and gait analysis results, collected as part of the authors' previous work. Finite element simulations were performed using the joint contact and muscle forces derived from two sources. The first approach was used the load case proposed by Dalstra et al. The second approach used joint contact and muscle forces predicted by a musculoskeletal model. Additionally, the musculoskeletal load case was discretised into 50 equal load steps and the results compared with the equivalent Dalstra load steps. RESULTS: The results showed that the contribution of the muscle forces resulted in minor differences in both the magnitude and distribution of the predicted acetabular micromotion (up to 4.01% in the mean acetabular micromotion) and interfacial bone strains (up to 10.34% in the mean interfacial bone strains). The degree of gait cycle discretisation had a significant influence on the acetabular micromotion with a difference of 20.89% in the mean acetabular micromotion. CONCLUSION: Outcomes of this study suggests that the acetabular cup micromotion and interfacial bone strains can be predicted just using the joint contact force. This helps to reduce the complexity of the finite element models by ignoring the contribution of muscle forces and the associated challenges of mapping these forces to the pelvis. However, the gait cycle needs to be adequately discretised to capture the micromotion at the bone-implant interface.

Gait biomechanics after proximal femoral nailing of intertrochanteric fractures.

Proximal femur fractures in the elderly are associated with significant loss of independence, mobility, and quality of life. This prospective study aimed to: (1) investigate gait biomechanics in intertrochanteric fracture (ITF) patients (A1 and A2 AO/OTA) managed via femoral nailing at 6 weeks and 6 months postoperative and how these compared with similarly aged elderly controls; and (2) investigate whether femoral offset shortening (FOS) and lateral lag screw protrusion (LSP) were associated with changes in gait biomechanics at postoperative time points. Hip radiographs and gait data were collected for 34 patients at 6 weeks and 6 months postoperatively. Gait data were also collected from similarly aged controls. FOS and LSP were measured from radiographs. Joint angles, external moments, and powers were calculated for the hip, knee, and ankle and compared between time points in ITF patients and healthy controls using statistical parametric mapping. The relationship between radiographic measures with gait speed, step length, peak hip abduction, and maximum hip abduction moment was assessed using a Pearson correlation. External hip adduction moments and hip power generation improved in the first 6 months postoperative, but differed significantly from healthy controls during single limb stance. LSP showed a moderate correlation with maximum hip abduction moment at 6 weeks postoperative (r = -0.469, p = 0.048). These results provide new detail on functional outcomes after ITF and potential mechanisms that functional deficiencies may stem from. Lag screw prominence may be an important factor in maintaining functional independence and minimizing the risk of secondary falls after ITF in the elderly.

Improvement in postural alignment is associated with recovery of mobility after complex acquired brain injury: An observational study.

PURPOSE: Determine how mobility changes over 6 months in people unable to walk at 8-weeks post-Acquired Brain Injury (ABI); if there is an association over time between postural alignment and mobility post-ABI; and if alignment after ABI becomes closer to healthy alignment over time. METHODS: Fourteen adults with ABI, evaluated over 6 months, and a reference sample of 30 healthy adults were studied. The primary measure for changes in mobility was the Clinical Outcome Variables Scale (COVS). Secondary measures were sit-to-stand, timed standing holding rails, independent walking speed and number of testing conditions achieved. The Functional Independence Measure (FIM) was scored at rehabilitation admission and discharge. To analyze postural alignment, participants were recorded in sitting and standing, each repeated holding rails, and walking if able. Three-dimensional kinematic data were used to quantify whole-body postural alignment, equal to mean segment displacements from the base of support in the transverse plane. Associations between three-dimensional kinematic alignment scores and COVS scores were calculated using Linear Mixed-Effects Models. RESULTS: Participants made significant improvements in COVS scores, most secondary mobility scores, and FIM scores over time (p ≤ .001). Relationships between increasing COVS scores and decreasing sitting and standing mal-alignment scores were statistically significant. Visual analysis of graphed segment positions indicated that sitting and standing alignment became more similar to healthy alignment over time; this was not clear for walking. CONCLUSION: Improvement in postural alignment may be a factor for improving mobility in people with severe impairments after ABI.

The effect of surgical change to hip geometry on hip biomechanics after primary total hip arthroplasty.

The aim of this study was to determine the effect of surgical change to the acetabular offset and femoral offset on the abductor muscle and hip contact forces after primary total hip arthroplasty (THA) using computational methods. Thirty-five patients undergoing primary THA were recruited. Patients underwent a computed tomography scan of their pelvis and hip, and underwent gait analysis pre- and 6-months postoperatively. Surgically induced changes in acetabular and femoral offset were used to inform a musculoskeletal model to estimated abductor muscle and hip joint contact forces. Two experiments were performed: (1) influence of changes in hip geometry on hip biomechanics with preoperative kinematics; and (2) influence of changes in hip geometry on hip biomechanics with postoperative kinematics. Superior and medial placement of the hip centre of rotation during THA was most influential in reducing hip contact forces, predicting 63% of the variance (p < 0.001). When comparing the preoperative geometry and kinematics model, with postoperative geometry and kinematics, hip contact forces increased after surgery (0.68 BW, p = 0.001). Increasing the abductor lever arm reduced abductor muscle force by 28% (p < 0.001) and resultant hip contact force by 17% (0.6 BW, p = 0.003), with both preoperative and postoperative kinematics. Failure to increase abductor lever arm increased resultant hip contact force 11% (0.33 BW, p < 0.001). In conclusion, increasing the abductor lever arm provides a substantial biomechanical benefit to reduce hip abductor and resultant hip joint contact forces. The magnitude of this effect is equivalent to the average increase in hip contact force seen with improved gait from pre-to post-surgery.

Setting up girls for success in fundamental motor skills: The role of balance in 8-10 year olds.

The purpose of this study was to explore the relationship between postural control and fundamental motor skills in girls. An observational cross-sectional study was conducted in 47 girls, aged 8-10 years. Postural control (postural sway centre of pressure) was evaluated during tandem stance, leading with dominant and non-dominant limbs with eyes open and closed, using an AMTI force platform. Fundamental motor skills were assessed using the Test of Gross Motor Development 2nd Edition, examining total, locomotor and object control scores. Data were analysed using linear regression, adjusted for body mass index percentile and household income. For locomotor skills, significant relationships were found with a number of postural sway outcomes for adjusted and unadjusted analyses (r - 0.287 to r - 0.425, p ≤ 0.042). Total motor skill score was significantly related to postural sway in the tandem dominant eyes closed condition for unadjusted and adjusted analyses (r ≥ -0.294, p ≤ 0.04). In conclusion, our findings indicate that postural control may be important for fundamental motor skill proficiency and movement quality in pre-adolescent girls, particularly for locomotor skills. Our study provides evidence supporting the clinical practice of assessing postural control in girls presenting with motor skill deficits.

Ex vivo assessment of surgically repaired tibial plateau fracture displacement under axial load using large-volume micro-CT.

Postoperative weight bearing has the potential to generate fragmental motion of surgically repaired tibial plateau fractures (TPFs), which may contribute to loss of fracture reduction. The effect of loading on the internal distribution of fragmentary displacements is currently unknown. The aim of this study was to determine the internal displacements of surgically repaired split TPFs due to a three-bodyweight load, using large-volume micro-CT imaging and image correlation. Fractures were generated and surgically repaired for two cadaveric specimens. Load was applied to the specimens inside a large-volume micro-CT system and scanned at 0.046 mm isotropic voxel size. Pre- and post-loading images were paired, co-registered, and internal fragmentary displacements quantified. Internal fragmental displacements of the cadaveric bones were compared to in vivo displacements measured in the lateral split fragments of TPFs in a clinical cohort of patients who had similar surgical repair and were prescribed pain tolerated postoperative weight bearing. The split fragments of cadaveric specimens displaced, on average, less than 0.3 mm, consistent with in vivo measurements. Specimen one rotated around the mediolateral axis, while specimen two displaced consistently caudally. Specimen two also had varying displacements along the mediolateral axis where, at the fracture site, the fragment displaced caudally and laterally, while the most lateral edge of the tibial plateau displaced caudally and medially. The methods applied in this study can be used to measure internal fragmental motion within TPFs.

Visualising knee loading patterns during kneeling and the development of a laboratory-based adaptation of the Aberdeen Weight-Bearing Test (Knee).

BACKGROUND: Information regarding the loading of key anatomical structures of the knee during kneeling would enhance existing functional tests, yet current visualisation methods are limited and require further development. AIMS: (1) Develop a knee loading visualisation technique to investigate loading patterns of the knee during kneeling; and (2) determine the utility of the technique in combination with vertical ground reaction forces and centre of pressure data in the lab-based Aberdeen Weight-Bearing Test (Knee) by assessing their reliability. METHODS: Fourteen healthy participants conducted kneeling tasks with and without knee pads across two testing sessions. Eight force-sensitive resistors were affixed to the right knee throughout different kneeling tasks: upright kneeling, and reaching forward, back, left, and right. A photo of the force-sensitive resistor configuration was used to generate participant-specific heat maps of knee loading. Two in-ground force platforms were used to measure vertical ground reaction forces and centre of pressure. RESULTS: The inferior patella tendon showed the highest proportion of activation during both bare and knee pad kneeling for all kneeling tasks. Knee pads reduced the repeatability of knee loading patterns. Force-sensitive resistor activation and vertical ground reaction force components of the lab-based Aberdeen Weight-Bearing Test (Knee) were shown to be reliable, whereas the centre of pressure data was unreliable. CONCLUSION: We have developed a lab-based technique for visualising knee loading using force-sensitive resistors. The combination of force-sensitive resistor activation and vertical ground reaction force data provides valuable insights into both the magnitude and locations of applied loads throughout kneeling.

Reoperation rates after proximal femur fracture fixation with single and dual screw femoral nails: a systematic review and meta-analysis.

Purpose: The purpose of this study was to investigate differences in aseptic reoperation rates between single or dual lag screw femoral nails,in the treatment of intertrochanteric fractures (ITF) in elderly patients. Methods: Electronic databases were searched for RCTs and prospective cohort studies treating elderly ITF patients with a single or dual screw femoral nails. Data for aseptic reoperation rates between single screw, dual separated screw and dual integrated screw devices were pooled using a random-effects meta-analysis with 95% CIs. Pooled proportions were compared using a N-1 chi-squared test. Complications contributing to aseptic reoperation rates were extracted, and the contribution of cut-out and periprosthetic fracture as a proportion of reoperations was analysed using a negative binomial regression model. Results: Forty-two (n = 42) studies were evaluated, including 2795 patients treated with a single screw device, 1309 patients treated with a dual separated screw device and 303 patients treated with a dual integrated screw device. There was no significant difference in aseptic reoperation rates between single and dual lag screw femoral nails of both separated and integrated lag screw designs. Moreover, complications of cut-out and periprosthetic fracture as a proportion of reoperations did not differ significantly between devices. Conclusion: The current evidence showed that aseptic reoperation rates were not significantly different between single and dual screw nails of a separated lag screw design. For dual integrated screw devices, due to insufficient evidence available, further high quality RCTs are required to allow for decisive comparisons with these newer devices.

Assigning trabecular bone material properties in finite element models simulating the pelvis before and after the development of peri-prosthetic osteolytic lesions.

Estimating strain distribution in the acetabulum before and after the development of peri-prosthetic osteolytic lesions secondary to total hip arthroplasty may assist with understanding the pathogenesis of this condition. This could be achieved by performing patient-specific finite element analysis of (1) total hip arthroplasty recipients with developed acetabular osteolytic lesions, and (2) models simulating the patient's pelvis and implant immediately after primary surgery. State of the art patient-specific total hip arthroplasty finite element analysis simulations obtain trabecular bone material properties from Hounsfield units within computed tomography (CT) scans of patients. However, this is not feasible when an implant is already in situ due to metal artefact disruption and, in turn, incorrectly reproduced Hounsfield units. Therefore, alternative methods of assigning trabecular bone material properties within such models were tested and strain results compared. It was found that assigning set material properties throughout the trabecular bone geometry was sufficient for the desired application. Simulating the primary implant and pelvis requires geometric and material based assumptions. Therefore, comparisons were made between strain values obtained from simulated primary models, from state of the art methods using material properties obtained from intact bone within a CT scan, and from models with osteolytic lesions. Strain values found using the finite element models simulating the pelvis before osteolytic lesion developed were considerably closer to those found using state of the art methods than those found for the bone loss models. These models could be used to determine relationships between strain distribution and factors such as bone loss.

Investigating and defining outcomes of suprapatellar versus infrapatellar intramedullary nailing of tibial shaft fractures: a protocol for a pilot randomised controlled trial.

BACKGROUND: Anterior knee pain is often reported following intramedullary nailing of tibial shaft fractures. The aetiology remains unclear, but the surgical approach may play an important role. To date, no biomechanically validated method exists to assess patient outcomes specific to anterior knee pain in this cohort. The central aims of this study are to (1) evaluate the feasibility of a full-scale randomised controlled trial (RCT) investigating the influence of surgical approach on intramedullary nailing of tibial shaft fractures (suprapatellar versus infrapatellar nailing), (2) explore differences in clinical outcomes between the approaches, and (3) explore the development of a biomechanically validated methodology for assessing post-operative anterior knee pain and knee function specific to intramedullary nailing of tibial shaft fractures. METHODS: This pilot study will follow a prospective randomised controlled design at the Royal Adelaide Hospital and The Queen Elizabeth Hospital (South Australia). This study aims to recruit 60 patients between 18 and 60 years old who will be randomly assigned to either the suprapatellar or infrapatellar approach following a decision for intramedullary surgical fixation by the treating surgeon. All nails in this study will be Stryker T2 Alpha nails. Patients will undergo standard radiograph, magnetic resonance imaging, and clinical assessments in-line with their standard operative care, and complete a number of patient-reported and performance-based outcome measures. Performance-based outcome measures will be assessed utilising three-dimensional motion capture techniques. Follow-up time points are 3, 6, 12, and 18 months. Feasibility outcomes include ability to meet enrolment and retention metrics, compliance with all questionnaires and assessment procedures, and the occurrence of any adverse events. The primary clinical outcome is the incidence of anterior knee pain at 12 months after surgery. DISCUSSION: This study will establish the feasibility and inform the design of a large-scale RCT. Evaluation of all clinical data and patient outcomes will lead to the development of a new tool for assessing patient outcomes in this cohort. Limitations of the study include an unpredictable enrolment rate and loss to follow-up, small sample size, and the unknown ability of three-dimensional motion analysis to pick up the effects of anterior knee pain after tibial nailing. TRIAL REGISTRATION: This trial was prospectively registered on the 7 February 2020 on ANZCTR, ACTRN12620000109909 .

An instrumented walker in three-dimensional gait analysis: Improving musculoskeletal estimates in the lower limb mobility impaired.

BACKGROUND: In three-dimensional (3D) gait analysis of individuals requiring a walking frame (walker), acquisition of artefact-free motion and force data is challenging. Without inclusion of handle-reaction forces alongside ground reaction forces, external forces used in musculoskeletal modelling are incomplete. This may increase dynamic inconsistencies between the model and measured motions and forces, thus, uncertainties in estimates of musculoskeletal load. RESEARCH QUESTION: To develop an instrumented walker and evaluate the effects of including handle-reaction forces on residual forces during musculoskeletal modelling. METHODS: An instrumented walker measuring handle-reaction forces synchronously with motion capture and ground reaction force data was developed. 3D gait analysis was conducted in ten elderly participants recovering from a proximal femur fracture and requiring a walker for ambulation. Joint kinetics and residual forces were calculated between two external load conditions: (1) external loads applied using only force platforms; or (2) external loads applied using force platforms and walker handle-reaction forces. RESULTS: Including handle-reaction forces reduced residual forces and improved estimates of musculoskeletal loads of the torso (P = <0.001). SIGNIFICANCE: A wide instrumented walker measuring handle-reaction forces allows for the gait analysis of individuals requiring a walker and improves reliability of musculoskeletal dynamics.

The Reproducibility of Bio-Acoustic Features is Associated With Sample Duration, Speech Task, and Gender.

Bio-acoustic properties of speech show evolving value in analyzing psychiatric illnesses. Obtaining a sufficient speech sample length to quantify these properties is essential, but the impact of sample duration on the stability of bio-acoustic features has not been systematically explored. We aimed to evaluate bio-acoustic features' reproducibility against changes in speech durations and tasks. We extracted source, spectral, formant, and prosodic features in 185 English-speaking adults (98 w, 87 m) for reading-a-story and counting tasks. We compared features at 25% of the total sample duration of the reading task to those obtained from non-overlapping randomly selected sub-samples shortened to 75%, 50%, and 25% of total duration using intraclass correlation coefficients. We also compared the features extracted from entire recordings to those measured at 25% of the duration and features obtained from 50% of the duration. Further, we compared features extracted from reading-a-story to counting tasks. Our results show that the number of reproducible features (out of 125) decreased stepwise with duration reduction. Spectral shape, pitch, and formants reached excellent reproducibility. Mel-frequency cepstral coefficients (MFCCs), loudness, and zero-crossing rate achieved excellent reproducibility only at a longer duration. Reproducibility of source, MFCC derivatives, and voicing probability (VP) was poor. Significant gender differences existed in jitter, MFCC first-derivative, spectral skewness, pitch, VP, and formants. Around 97% of features in both genders were not reproducible across speech tasks, in part due to the short counting task duration. In conclusion, bio-acoustic features are less reproducible in shorter samples and are affected by gender.

EMG-Informed Neuromusculoskeletal Models Accurately Predict Knee Loading Measured Using Instrumented Implants.

OBJECTIVE: Using a musculoskeletal modelling framework, we aimed to (1) estimate knee joint loading using static optimization (SO); (2) explore different calibration functions in electromyogram (EMG)-informed models used in estimating knee load; and (3) determine, when using an EMG-informed stochastic method, if the measured joint loadings are solutions to the muscle redundancy problem when investigating only the uncertainty in muscle forces. METHODS: Musculoskeletal models for three individuals with instrumented knee replacements were generated. Muscle forces were calculated using SO, EMG-informed, and EMG-informed stochastic methods. Measured knee joint loads from the prostheses were compared to the SO and EMG-informed solutions. Root mean square error (RMSE) in joint load estimation was calculated, and the muscle force ranges were compared. RESULTS: The RMSE ranged between 192-674 N, 152-487 N, and 7-108 N for the SO, the calibrated EMG-informed solution, and the best fit stochastic result, respectively. The stochastic method produced solution spaces encompassing the measured joint loading up to 98% of stance. CONCLUSION: Uncertainty in muscle forces can account for total knee loading and it is recommended that, where possible, EMG measurements should be included to estimate knee joint loading. SIGNIFICANCE: This work shows that the inclusion of EMG-informed modelling allows for better estimation of knee joint loading when compared to SO.